The control of proliferation of granulosa cells by gonadotropin (FSH LH) and mitogenic agents (OGF, FGF) will be studied in tissue culture. The effect of the mitogenic agents and gonadotropin on the proliferation as well as the differentiation of granulosa cells into luteal cells will be compared. The mitogenic effect of those agents will then be examined using follicles maintained in organ culture and intact ovaries in vivo. We will determine whether FGF could be involved in the luteinization process by controlling the proliferation of capillaries which invade the granulosa cell layers after the basement membrane breakdown.